This invention relates to new and useful improvements in methods and apparatus for weaning patients from continuous mechanical ventilators.
There are two methods to wean a patient with ventilatory failure away from continuous mechanical ventilation. The oldest method involves simply taking the patient off the ventilator for increasing periods. While off the ventilator, oxygen and humidity to the patient is provided by a heated nebulizer requiring a second ventilatory circuit and equipment.
A newer method called intermittent mandatory ventilation (IMV) essentially combines the action of both circuits and while allowing the patient to breathe at his own rate and depth, occasionally at a preset rate superimposes large mandatory breaths from the ventilator. I.M.V. is useful in patients with airways obstruction or neurological problems but requires complex tubing connections, there is assynchrony between patient and ventilator and there is difficulty in monitoring rate and volume of each breath. A variation of this method of weaning is synchronized I.M.V. (S.I.M.V.) whereby the mandatory large breath is synchronized to the patient's inspiratory effort.
An ideal method of weaning should allow synchrony between the patterns of breathing of the patient and ventilator, it should use the ventilator to provide oxygen and humidity for both assisted and unassisted breaths, and it should allow monitoring of the breathing pattern that results.